Detection and identification of hazardous or controlled substances in body fluid or tissue samples is an important part of clinical and forensic medicine. The process is often complicated by the large number of endogenous components present in a typical biological sample from which a target substance, or substances, must be isolated. It is desirable for such determinations to be carried out rapidly, with a minimal amount of sample preparation and extraction steps. High sample recovery is needed in detecting trace amounts and for accuracy in quantitation if necessary.
Solid phase extraction (SPE) has largely replaced liquid-liquid extraction methods due to greater convenience and, generally, greater recovery of the substances of interest. Because it is preferable for the same equipment, materials and procedures to be used on the greatest number of different substances to be determined, "mixed mode" extraction media, which include both hydrophobic and polar components, have been introduced. These allow multiple types of interactions with various portions of a drug molecule, i.e. with both hydrocarbon regions and polar or charged sites. In the case of cation- and anion-exchange resins, different resins are used for differently charged analytes.
Typically, however, the use of such mixed-mode supports has required rather complex extraction procedures, using sequences of extraction steps and/or complex solvent mixtures, to selectively bind the compounds of interest, elute contaminants, and then selectively elute the target compounds. Even with the use of such procedures, the recovery of an analyte substance may be low, and interfering endogenous substances may still be co-eluted. Contamination from the support itself can also interfere with the determination.
It is therefore desirable to provide a single support and simple extraction protocols suitable for a wide range of substances to be analyzed, particularly for the detection of drugs of abuse in body fluid samples. Ideally, the extracts are suitable, without further purification, for gas chromatographic (GC), GC-MS (mass spectrometry), or HPLC (high performance liquid chromatography) analysis, thus allowing high turnover with minimal contamination of analytical equipment.